Bought my first mopar 73’ Duster and the bottom of the air filter pan is black (right above the carb). Any tips on how the 4bbl should be adjusted

Air cleaner lid is black cause of backfires. Get back with timing #s also hood clearance causes issues with a-bodys and people try and fix with drop bases like yours small height air filters etc. which act as a full time choke. Notice your vent tubes are removed to allow for that low profile system. Try and fit the highest air filter and test with puddy with hood closed for clearance. You may have engine issues causing backfires. Nice car, good luck